MPI_WAITANY, MPI_Waitany

Purpose

Waits for any specified nonblocking operation to complete.

C synopsis

#include <mpi.h>
int MPI_Waitany(int count,MPI_Request *array_of_requests,
    int *index,MPI_Status *status);

C++ synopsis

#include mpi.h
int MPI::Request::Waitany(int count, MPI::Request array[]);

#include mpi.h
int MPI::Request::Waitany(int count, MPI::Request array[],
                          MPI::Status& status);

FORTRAN synopsis

include 'mpif.h' or use mpi
MPI_WAITANY(INTEGER COUNT,INTEGER ARRAY_OF_REQUESTS(*),INTEGER INDEX,
      INTEGER STATUS(MPI_STATUS_SIZE),INTEGER IERROR)

Description

This subroutine blocks until one of the operations associated with the
active requests in the array has completed. If more than one operation can
complete, one is arbitrarily chosen. MPI_WAITANY returns in index the index
of that request in the array, and in status the status of the completed
operation. When the request is allocated by a nonblocking operation, it is
deallocated and the request handle is set to MPI_REQUEST_NULL.

The array_of_requests list can contain null or inactive handles. When the
list has a length of zero or all entries are null or inactive, the call
returns immediately with index = MPI_UNDEFINED, and an empty status.

MPI_WAITANY(count, array_of_requests, index, status) has the same effect as
the execution of MPI_WAIT(array_of_requests[i], status), where i is the
value returned by index. MPI_WAITANY with an array containing one active
entry is equivalent to MPI_WAIT.

Passing MPI_STATUS_IGNORE for the status argument causes PE MPI to skip
filling in the status fields. By passing this value for status, you can
avoid having to allocate a status object in programs that do not need to
examine the status fields.

When one of the MPI wait or test calls returns status for a nonblocking
operation request and the corresponding blocking operation does not provide
a status argument, the status from this wait or test call does not contain
meaningful source, tag, or message size information.

When you use this subroutine in a threads application, make sure that the
wait for a given request is done on only one thread. The wait does not have
to be done on the thread that created it. See IBM Parallel Environment for
AIX: MPI Programming Guide for more information on programming with MPI in
a threads environment.

Parameters

count
     is the list length (integer) (IN)
array_of_requests
     is the array of requests (array of handles) (INOUT)
index
     is the index of the handle for the operation that completed (integer)
     (OUT)
status
     status object (Status) (INOUT). Note that in FORTRAN a single status
     object is an array of integers.
IERROR
     is the FORTRAN return code. It is always the last argument.

Notes

The array is indexed from 0 in C and from 1 in FORTRAN.

Errors

A GRequest free function returned an error

A GRequest query function returned an error

Invalid status ignore value

Invalid form of status ignore

Invalid count
     count < 0

Invalid requests array

Invalid request(s)

Truncation occurred

MPI not initialized

MPI already finalized

Develop mode error if:

Illegal buffer update (ISEND)

Inconsistent datatype (MPE_I collectives)

Inconsistent message length (MPE_I collectives)

Inconsistent op (MPE_I collectives)

Match of blocking and non-blocking collectives (MPE_I collectives)

Related information

     MPI_TESTANY
     MPI_WAIT